In recent years, backlight units including conventional cold cathode fluorescent tubes (CCFLs) and backlight units including a plurality of light emitting diodes (LEDs), which are hereinafter referred to as LED backlights, are widely used as backlight units (light emitting devices) for display devices such as liquid crystal display devices.
In general, forward voltages of LED components vary from one another due to variations among the LED components. In an LED backlight unit, lines of LED components are connected in parallel to each other. The LED components in each line are connected in series and driven with a common drive voltage. During the driving of the LED components, forward voltages Vf of the LED component lines vary due to the variations among the LED components. The variations in forward voltage Vf of the LED component lines cause an unnecessary drive power loss. A technology for reducing such an unnecessary drive power loss is disclosed in Patent Document 1. Differences in drive voltage caused by variations in forward voltage Vf of LED component lines are determined and a common drive voltage applied to the LED component lines is properly adjusted, that is, negative feedback control is performed.